Flameproof composition



Search mm UNETED STATES FLAMEPROOF COMPOSITION Martin Eli Cupery,Wilmington, DeL, assignor to E. I. du Pont de Nemours & Company,Wilmington, Del., a. corporation of Delaware FFICE No Drawing.Application February 21, 1939, Serial No. 257,760

9 Claims. (CI. 9168) This invention relates to the flameproofing ofillustrated by the following examples, wherein organic combustiblematerials, particularly texparts given are by weight. There are ofcourse tile and cellulosic materials. many forms of the invention otherthan these This invention has as an object the provision specificembodiments.

of a novel and useful fire-retardant for com- Example I 5 bustibleorganic materials. A further object is the provision of a fire-retardantfor textiles and n hundred fifty (150) parts of urea hearted jcellulosic materials. A still further object is the to about o is mixed-With 30 Parts Of D W- provision of a combined softening andfir-e-redared- Sulfamic acid- The mixture readily.fuses 10 t m agent,for teXti1eS other Objects 1 to a clear melt at about 110- C. Anadditional 10 pear herejnaften 164 parts of sulfamic acid is next addedwith x These objects are accomplished by the f 11 stirring while thefused mixture is maintained at \i m; t ing invention which comprisesnon-volatile com- 110 130 Upon ther heating to 120 C. bustible organic,and particularly cellulosic, maan exothermic reaction begins, a aConsider- 15 terials containing, in amount sufficient to act as ableamount of gas is evolved. Cooling is re- 15 a fire-retardant, a fusionproduct of urea and quired to keep temperature below Smfamjc acid Afterstanding at 140-l50 C. for ten minutes,-

The invention in t prefer d form is the mixture is cooled and thentreatedwith 300 ticed as follows. The fire-retardant is first prepartsof ice watel" A Small amount" of product pared by heating one 11101 ofsutfamie acid with remains undissolved and is separated by filtration.20

from 5 t 3 mole of urea, t 'te t t After neutralizing the filteredsolution with conwhich reaction takes place as evidenced by theCentrated ammonium hydroxi eit is diluted With evolution of heat whichtemperature is ordinarily Water to a SOTIIfiOII- ge ated cellulose at1east Some 15 above the point at which sheeting in the gel form isimmersed for one mint mixture fuse and preferably higher t ute in thissolution, and is then removed and cooling externally to dissipate theheat of reacdried under Slight te s n at 100 C. for 10 mint T minimumtemperature 111 usuany he utes. The dried cellulose sheet, whichcontains about 120 C. The reaction is generally complete about 0f the fieta d t, is e y ansithi one hour Th d t i th dissolved parent and showsno crystallization of fire-rein water, any undissolved material filteredoff, Trardant even upon Storage at 5 C. and 50% 30 and the solution, ifacidic, neutralized with amrelative humidity for SeVeral mont s- Thetreatmonia or alkali. This neutral aqueous solution ed Sheet is a oof t0the extent at t is then applied directly to the combustible ma- 1111568Only at the P t O Contact with a flame terial. The amount which can beabsorbed will While showing no tendency t pr pa ate a flame. naturallydepend on the nature of the material. At a relative humidity a v 0%, thefire-re- 35 If relatively dense, the aqueous solution should tardantalso has a very definite softening action preferably be concentrated,while if porous, more 011 the regenerated cellulose sheet. 7 dilutesolutions are suitable. The regulation of Example II the concentrationof the solut1on 1s a convenient 40 means of controlling the amount offire-retarol- Nmety (90) parts of urea 15 heatedto 40 ant applied. Theamount to apply win of Course and sulfamic acid slowly added to the meltwith depend upon t degree of flame-resi t n stirring until 97 parts ofthe acid has been added. et Cotton fabri s paper, and regenerated Themass forms a clear melt which foams slightly '3celluloseofilmsarfi..IQRQQ TFQEPWEJY ame roof" Wlth some evolution ofammonia. After m i Wpphcatmn thggetolflo'f l0 18% weight of taming atemperature of 14b C. for ten mmu-tes t mth'ifiaht fiT this result,after the additlon of the acid, the mass is cooled tions of about 5-10%are generally used. and dissolved in enough r? to give 1000 p rts Thenature of t reaction or reactions taking of solution. Titration of asample of the solution place in making t fire-.retardant are not knownusing phenolphthalein as indicator shows that t t is believed, t t acQmple mixture f about 80% of the sulfamic acid is neutralized by 5 uctsis formed. Titration of the dissolved fusion the fuSiQIl reaction withAfter neutralizing product indicates that th sulfamic a id is new withammonia, the solution is dilutedwith water tralized and that a moreextensive reaction than 1:0 give Concentration of fi eta dant. Cotmereformation of urea sulfamate takes place. ton broadcloth s r ndflameproof w n m- V The more detailed practice of the invention is p qggqg y f h by weight O W 5?" V geuw 0.; Ne s.

retardant, based on the original weight of cloth. The treated fabricshows no increased harshness or stiffness on drying and no objectionablecrystallization or surface eiilorescence upon storage.

Equally good results are obtained upon treating other fabrics, such ascotton voile, muslin, linen and viscose rayon fabrics as in Example II.Similarly, various types of paper such as hand. towel paper, tissuesheet, crepe paper, wrapping paper, and the like are made fiameproof byimpregnating with 10 to 15% by weight of the above fire-retardant.

Example III One hundred eighty (180) parts of urea is fused with 97parts of sulfamic acid by gradually heating the mixture to 160 C. andmaintaining the latter temperature for fifteen minutes. Ammonia isslowly evolved from the melt. The melt is then poured into 1850 parts ofcold water. The small residue which remains undissolved is removed byfiltration and the filtrate neutralized with ammonia. The resultingsolution contains about 13% of fire-retardant. Cotton voile impregnatedwith this solution absorbs about 10-13% of the fire-retardant and ismade flameproof in the sense that it will not propagate a flame whenignited but will only be charred at the point of actual contact with thefiame.

Various fabrics such as muslin, linen, viscose rayon and the like, aswell as paper and transparent regenerated cellulose sheet, can be madefiameproof when treated with the product of Example III in the mannerdescribed.

The examples given describe fusions of urea with sulfamic acid asfollows:

Parts Mol ratio T Time heated Example empetat maximum ature t Urea AcidUrea Acid tempera ure 0. Minutes 150 194 1.25 1 150 These proportions,i. e., 1.25 to 3 mols urea per mol of acid, are preferred although molratios as low as 1:1 or as high as 5:1 (ureazacid) may be used.Proportions of urea below 1.25 mols give difficult fusions and yieldexcessive biuret as by-product and will not generally be used. As theamount of urea exceeds about 3 mols, the resultant fusion productsbecome less and less effective as fire-retardants, and when it exceedsabout 5 mols, they are no longer very practical. This latter isespecially evident with sheet gel regenerated cellulose.

The reaction which takes place is exothermic and adequate provision mustbe made to prevent the temperature from exceeding about 160 C. as highertemperatures cause excessive formation of biuret. On the other hand, themixture must be heated sufiiciently to start the reaction between ureaand sulfamic acid. A temperature of about C. will in general be suitablefor starting the reaction. When high proportions of urea are employed,e. g. 3 mols urea to one mol acid, the minimum temperature for startingthe reaction and the maximum temperature at which the reaction iscarried out may be somewhat higher than corresponding temperatures whenlow proportions of urea to acid, e. g. 1.25 mols urea to one mol acid,are used.

Because the reaction proceeds rapidly, a period of only 10 to 15 minutesis required to cause it to proceed to approximately 80% completion, asis indicated by the neutralization of the sulfamic acid. It is notpractical to carry the reaction further for a longer period of time asexcessive formation of biuret will take place as the reaction time isincreased. However, if the maximum reaction temperature is lowered, thetime of reaction may be increased proportionately but the results, withrespect to the formation of by-product biuret, will be very similar.

The procedure for dissolving the product and diluting the solution toproper concentration is easily carried out by anyone skilled in the art.Likewise simple experimentation will readily indicate the concentrationof solution which is optimum for impregnating a given material and theproper retention of fire-retardant which is required in order to producethe desired degree of fire and flame resistance.

The present urea-sulfamic acid fusion products may be used incombination with known fireretardants such as ammonium sulfate, ammoniumchloride, ammonium bromide, ammonium fiuoride, ammonium carbonate,ammonium phosphate, boric acid, sodium borate, sodium silicate, sodiumcarbonate, and the like. Fire-retarding effects may also be obtainedwhen the fusion product is applied by methods other than impregnationfrom aqueous solution. For example, powdered crystals may be dusted upona damp surface or surface treated with adhesive; the fusion product maybe applied from solution or suspension in an organic liquid; or in thecase of a combustible liquid, the fusion product may be incorporated bymixing or milling.

An outstanding advantage of the present sulfarnic acid-urea fusionproducts over the more commonly used prior art flameproofing agents fortextile fabrics is that they do not cause the harshness which normallycharacterizes fabrics treated with the prior art materials, and in manyinstances they have a softening effect of their own. As flameproofingagents for regenerated cellulose film, the fusion products have anadvantage over prior art materials in that, even when present in thefilm in amounts up to about 18%, they do not crystallize out on thesurface of the film under ordinary atmospheric conditions (24 C. and 35%relative humidity) as is characteristic of prior art fiameproofingmaterials. Under favorable conditions, the amount may be as high as 25%without crystallizing out. Furthermore, the present fusion products notonly render cellulose and its manufactures (film, thread, fabrics, caps,

bands, sponges, etc.) fiameproof, but also impart to these materials acertain degree of softness. Hence they may also be used, either alone orin conjunction with glycerol or softener, as combined softening andfiameproofing agents. In the case of rayon, the fusion product may beadded with good results to the viscose, to the undried sheet, or to thedried sheet before or after application of moistureproofing lacquers,such as those of Charch and Prindle (U. S. 1,737,- 187 and 1,826,696).The fact that the moistureproofing lacquer may contain highlyinflammable substances does not seem to make any appreciable difference.The cellulose thread, fabric, or film which has been impregnated withthe fusion product may be stored for prolonged periods Withoutdeterioration.

The sulfamic acid-urea fusion products may also be employed asfire-retardants for other cellulosic materials, which term is intendedto inother common MISCELLANEOUS PRODUCTS. I

clude cellulose derivatives as well as cellulose, and manufactures ofboth. Examples of such additional cellulosic materials are celluloseesters such as the nitrate, acetate, propionate, butyrate, andphthalate, and cellulose ethers such as methyl-, ethyl-, benzyl-,crotyl-, hydroxyethyland carboxymethylcelluloses. These cellulosederivatives may be undegraded or highly degraded, of any degree ofsubstitution, and of any degree of water-sensitivity.

Fabrics that have been treated with the fusion product and thus renderedfire-resistant may be subsequently rubberized and the rubber coatingvulcanized under the usual conditions (about 2 to 3 hours at about 120C.) without appreciable tendering of the fabric.

The sulfamic acid-urea fusion products are effective as fire-retardantsso far as is known, for any non-volatile combustible organic materialwhatever. Cellulosic materials, with which the advantages of thisinvention are most apparent, have been discussed in detail. Othermaterials are proteins and their manufactures such as films andfilaments from casein, gelatin, zein, gliadin, edestin and the like;natural and synthetic resins such as rosin, ester gum, alkyd resins,polymeric esters of acrylic and methacrylic acid, vinyl resins, etherresins, and films and plastics made therefrom; natural and syntheticoils and films therefrom, such as linseed oil, linoxyn, anddivinylacetylene polymer; rubber and synthetic rubbers; leather, silk,and wool; and any combustible substance whatever.

The concentration of fire-retardant employed may vary depending upon thetype and nature of material to be treated and the degree offlameproofness which is desired. In general, a retention of 8 to 15% byweight of fire-retardant is adequate to fiameproof cellulosic materialsso that they will not propagate a flame.

The expression regenerated cellulose in gel form" used in the exampleshas reference to a sheet of cellulose which has been regenerated in awell-known manner from a solution of cellulose xanthate (viscose),washed and purified, but not dried. Regeneratea cellulose in gel formmay also be obtained from solutions of suitable cellulose derivativessuch as cuprammonium solutions.

The above description and examples are intended to be illustrative only.Any modification of or variation therefrom which conforms to the spiritof the invention is intended to be included within the scope of theclaims.

I claim:

1. An article resistant to fire comprising a substantially, non-volatilecombustible organic material and, as a fire-retardant therefor, thewater soluble product obtained by reaction of urea and sulfamic. acid inthe fused state.

2. An article resistant to fire comprising a cellulosic material and, asa'fire-retardant therefor, the water-soluble product obtained byreaction of urea and sulfamic acid in the fusedrstate.

3. Transparent regenerated cellulose sheet material containing, an. firertardant therefor, the water soluble product obtained by reaction ofurea and sulfamic acid in the fused state.

4. An article resistant to fire comprising a non-volatile combustibleorganic material and, as a fire-retardant therefor, the water solubleproduct obtained by the reaction of one to five mols of urea with onemol of sulfamic acid at a temperature of from 120 to 160 C.

5. An article resistant to fire comprising a cellulosic material and, asa fire-retardant therefor, the water soluble product obtained by thereaction of one to five mols of urea with one mol of sulfamic acid at120 to 160 C.

j Transparent regenerated cellulose sheet material containing, asaQre-retardanttherefor, the water soluble producto'btained by thereaction of one to five mols of urea with one mol of sulfamic acid at120 to 160 C.

7. An article resistant to fire comprising a nonvolatile combustibleorganic material and, as a fire-retardant therefor, the water solubleproduct obtained by the fusion of five to twelve mols of urea with fourmols of sulfamic acid at 120 to 160 C.

8. An article resistant to fire comprising a cellulosic material and, asa fire-retardant therefor, the water soluble product obtained by thefusion of five to twelve mols of urea with four mols of sulfamic acid at120 to 160 C.

9. Transparent regenerated cellulose sheet material containing, as afire-retardant therefor, the water soluble product obtained by thefusion of five to twelve mols of urea with four mols of sulfamic acid at120 to 160 C.

MARTIN ELI CUPERY.

